The purpose of this application is to permit continuing support for the multidisciplinary investigative program in cardiovascular research at the Massachusetts General Hospital which aims to increase the basic understanding of cardiovascular function and to apply this knowledge to improving the prevention and management of cardiovascular diseases. This program involves the joint investigative talents and physical facilities of several important laboratories of the Departments of Medicine and Surgery; The Cardiac, Cardiac Catheterization, Cardiac Surgery, Cardiorenal, Hypertensive, Vascular Surgery and Pulmonary Units. Although this application brings together a diversity of investigators from a number of disciplines there is a general theme threaded through the application. All are related to problems of the circulation - be they due to the heart, the function of which is impaired by coronary vascular disease, or by digitalis intoxication; be they of the peripheral circulation as ischemic renal injury, or increased pulmonary vascular resistance with hypoxia; or be they studies of the energy requirements of ion transport which depend on the integrity of the supply of oxygen and substrate to the tissues, and hence on circulation. The proposals are a mixture of studies into causation of physiologic and clinical phenomena and into the management of their pathologic consequence.